Neurostimulation site screening

ABSTRACT

The disclosure describes a process for non-invasively screening a patient to select a stimulation site for treatment of head, neck or facial pain and tension symptoms caused by disorders such as occipital neuralgia. The screening process involves application of a transcutaneous stimulation screening device, a percutaneous micro-electrode screening device, and a temporary implantable screening device to the patient to select a site for chronic implantation.

TECHNICAL FIELD

The invention relates to medical devices, and more particularly, tomedical devices for delivery of neurostimulation.

BACKGROUND

Implantable neurostimulators are used to deliver therapy to patients totreat a variety of symptoms or conditions such as chronic pain, tremor,Parkinson's disease, epilepsy, incontinence, sexual dysfunction, orgastroparesis. A neurostimulator delivers neurostimulation therapy viaone or more leads that include electrodes located proximate to thespinal cord, pelvic nerves, or stomach, or within the brain of apatient. In general, the implantable neurostimulator deliversneurostimulation therapy in the form of electrical pulses.

Depending on the application for which they are implanted in a patient,neurostimulators may include a variety of electrical and mechanicalcomponents. Typically, a neurostimulator includes a rigid housing thathouses all of its components, which are generally fragile, to protectthe components from forces and fluids to which they would otherwise beexposed when implanted within the human body. The size and shape of aneurostimulator housing is dependent on the sizes and shapes of thecomponents of the neurostimulator.

A neurostimulator is typically implanted within the abdomen, upperpectoral region, or subclavicular region of a patient. Leads orcatheters are used to deliver therapy or monitor a physiologicalparameter at a remote location of the body. The leads or cathetersextend from the neurostimulator housing for placement at a target site.

Implantation and positioning of leads and catheters can be difficult andtime-consuming from the perspective of a surgeon, particularly where theneurostimulator is located a significant distance from the treatment ormonitoring site. The increased surgical time, increased surgical trauma,and increased amount of implanted material associated with the use ofleads and catheters can increase the risk to the patient ofcomplications associated with the implantation of a neurostimulator.

In addition, selection of an efficacious target site for deployment of alead or catheter is difficult. Some leads include an array of electrodesthat can be selectively activated to target different nerve sites orcreate different energy fields. Once a lead is in place, however,repositioning of the lead is generally undesirable. In particular, thepatient ordinarily must undergo an additional surgical procedure withassociated risks. Accordingly, selection of a nerve site appropriate fortherapeutic efficacy continues to be a concern.

SUMMARY

In general, the invention is directed to devices and methods fornon-invasively screening a patient to select a stimulation site fortreatment of head, neck, or facial pain or tension, including pain ortension caused by occipital neuralgia. The stimulation site maygenerally reside within the upper cervical region of the spine, e.g.,C1-C4, and may target occipital nerves and branches in that region. Aneurostimulator can be implanted at the selected stimulation siteadjacent a neuralgic region of the patient, and deliver neurostimulationtherapy to treat pain and tension symptoms.

The screening devices and methods apply one or more of a transcutaneousstimulation screening device, a percutaneous micro-electrode screeningdevice, and a temporary implantable screening device to the patient toselect a site for chronic implantation. A health care provider mayperform imaging, such as magnetic resonance imaging (MRI), to select anepidermal region adjacent a neuralgic region of the patient. Forexample, the epidermal region may be within the back of the neck, in theupper cervical region of the spine of the patient, adjacent theoccipital nerve.

A transcutaneous stimulation screening device applies an electrode arrayto the epidermal region of the patient and applies electricalstimulation at difference positions across the electrode array. As thestimulation moves across the electrode array, the patient providesfeedback concerning the efficacy of the stimulation. The feedback may bein the form of a pain assessment, obtained for several stimulationregions within the epidermal region. Based on the feedback, the healthcare provider selects a stimulation region for percutaneous stimulation,or temporary or chronic implantation of an implantable neurostimulator.

A percutaneous micro-electrode screening device applies amicro-electrode needle array to the selected stimulation region tolocalize the region to a stimulation site. In this way, a more specificstimulation site may be selected for the implantation of aneurostimulator, e.g., following identification of a general stimulationregion using the transcutaneous stimulation screening device describedabove. Needle electrodes in the micro-electrode needle array may formbipolar electrode pairs or operate as unipolar electrodes in conjunctionwith a reference electrode that may be placed on the skin of thepatient, or a reference electrode incorporated within the needle arrayat a distance from the unipolar needle electrodes.

A temporary implantable screening device may be subcutaneously implantedat the localized stimulation site to test the efficacy of thestimulation region or site selected in the transcutaneous orpercutaneous screening. The temporary implantable screening device maybe implanted at a stimulation region identified using the transcutaneousstimulation screening device or a stimulation site identified using thepercutaneous micro-electrode array. The temporary implantable screeningdevice may comprise a battery with a lifetime of at least one day tosupport temporary stimulation of the neuralgic region of the patient.

In one embodiment, the invention is directed to a method comprisingapplying transcutaneous electrical neurostimulation to multiplestimulation regions on an epidermal surface adjacent a neuralgic regionof a patient, selecting one of the stimulation regions based onperceived efficacy of the transcutaneous electrical neurostimulation inthe selected stimulation region, applying percutaneous electricalneurostimulation to multiple stimulation sites within the selectedstimulation region, and selecting one of the stimulation sites based onperceived efficacy of the percutaneous electrical neurostimulation inthe selected stimulation site.

In another embodiment, the invention is directed to a neurostimulationscreening device comprising a transcutaneous electrical neurostimulationelectrode array for application to an epidermal region adjacent aneuralgic region of a patient, and a controller coupled to thetranscutaneous electrical neurostimulation electrode array toselectively apply stimulation energy to different combinations ofelectrodes within the array at different stimulation regions, and recordpatient feedback relating to perceived efficacy of the differentcombinations.

In an additional embodiment, the invention is directed to aneurostimulation screening device comprising an array of percutaneousneedle electrodes for penetration of an epidermal region adjacent aneuralgic region of a patient, and a controller coupled to the needleelectrodes to selectively apply stimulation energy to differentcombinations of the needle electrodes within the array at differentstimulation sites.

In another embodiment, the invention provides a neurostimulationscreening device comprising a transcutaneous electrical neurostimulationelectrode array for application to an epidermal region adjacent aneuralgic region of a patient, an array of percutaneous needleelectrodes for penetration of the epidermal region adjacent theneuralgic region of a patient, and a controller to selectively applystimulation energy to different combinations of electrodes within thetranscutaneous electrical neurostimulation electrode array at differentstimulation regions, and selectively apply stimulation energy todifferent combinations of the needle electrodes within the array atdifferent stimulation sites within one of the stimulation regions.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a transcutaneous stimulationscreening device.

FIG. 2 is a side view of an electrode array patch shown in FIG. 1.

FIG. 3 is a conceptual diagram illustrating one example of a controllerfor use with the screening device from FIG. 1.

FIG. 4 is a block diagram illustrating the screening controller of FIG.1 in greater detail.

FIG. 5 is a schematic diagram illustrating an example of amicro-electrode screening device.

FIG. 6 is a schematic diagram illustrating a temporary implantablescreening device.

FIG. 7 is a schematic diagram illustrating an example chronicneurostimulator subcutaneously implanted in an occipital nerve region atthe back of a neck of a patient.

FIG. 8 is a flow chart illustrating a screening process to select astimulation site for treatment of a neuralgic region of a patient.

FIGS. 9A and 9B respectively illustrate a top view and a side view of achronically implantable neurostimulator.

FIG. 10 is a schematic diagram illustrating an exemplary bottom view ofa neurostimulator in accordance with an embodiment of the invention.

FIG. 11 is an exemplary side view of the neurostimulator of FIG. 10.

FIG. 12 is a schematic diagram illustrating another exemplary bottomview of a neurostimulator in accordance with another embodiment of theinvention.

FIG. 13 is a schematic diagram illustrating another exemplary bottomview of a neurostimulator in accordance with an embodiment of theinvention.

FIG. 14 is a schematic diagram illustrating an exemplary tool forinsertion or removal of a neurostimulator.

FIGS. 15A and 15B respectively illustrate a top view and a side view ofa neurostimulator.

FIG. 16 is a block diagram illustrating an exemplary control moduleincluded in an on-site neurostimulator for the treatment of neuralgiaexperienced by a patient.

FIG. 17 illustrates a neurostimulator for treatment of neuralgiaexperienced by a patient.

FIG. 18 is a schematic diagram illustrating an exemplary external viewof a neurostimulator in accordance with an embodiment of the invention.

FIG. 19 is a schematic diagram illustrating another exemplary externalview of a neurostimulator in accordance with an embodiment of theinvention.

FIG. 20 is a schematic diagram illustrating the neurostimulator of FIG.19 in a slightly bent position to better conform to an implantationsite.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram illustrating a transcutaneousneurostimulation screening system 2. The transcutaneous stimulationscreening system 2 may be used to non-invasively select a stimulationregion to treat head ache, neck ache, or facial pain or tension,including pain or tension caused by occipital neuralgia. Theneurostimulation may generally be directed to the upper cervical regionof the spine, e.g., C1-C4, and may target occipital nerves andperipheral nerve branches in that region. Also, in some cases, system 2may stimulate muscle tissue instead or, or in addition to, nerves in theupper cervical region.

System 2 may be applied to treat symptoms of occipital neuralgia.Occipital neuralgia is a chronic pain disorder caused by irritation orinjury to the occipital nerve, which is located at the back of the neck.Occipital neuralgia may cause pain, often described as throbbing andmigraine-like, originating at the nape of the neck and spreading up andaround the forehead and scalp. Occipital neuralgia can result fromphysical stress, trauma, or repeated contraction of the muscles of theneck. Although application of the invention to occipital neuralgia willbe described herein for purposes of example, the invention may beapplied to alleviate pain or tension caused by other neurologicaldisorders in the upper cervical region.

The transcutaneous stimulation screening system 2 illustrated in FIG. 1is used to select a stimulation region adjacent a neuralgic region of apatient 4. Upon selection of the stimulation region, a neurostimulator(not shown in FIG. 1) may be subcutaneously implanted in the stimulationregion on a chronic basis to substantially alleviate the painexperienced by the patient. As will be described, the neurostimulatormay comprise a neurostimulator device with a miniaturized form factorand a low profile to allow implantation at the stimulation site. Foroccipital neuralgia, the neurostimulator may be subcutaneously implantedat a stimulation site generally located in the back of the neck of thepatient.

Alternatively, additional screening can be performed to narrow thestimulation region to a preferred stimulation site. For example, anadditional stimulation screening system, in the form of a percutaneousneedle electrode array, may be applied to patient 4 to more preciselyidentify a stimulation site prior to chronic implantation of aneurostimulator. As a further alternative, application of thetranscutaneous stimulation screening system may be followed by thepercutaneous needle electrode array, and then by a temporaryneurostimulator implanted at the stimulation site, prior to implantationof a chronic neurostimulator. The temporary neurostimulator may providea trial screening period to evaluate the efficacy of neurostimulation inthe relief of symptoms of occipital neuralgia. These alternatives willbe described in further detail below.

With further reference to FIG. 1, transcutaneous stimulation screeningsystem 2 includes an electrode array patch 6 and a screening controller12. Electrode array patch 6 may be applied to an epidermal region 8 of apatient's head, adjacent to a neuralgic region. A caregiver, such as aphysician or clinician, may perform imaging of the head of the patient4, e.g., using magnetic resonance imaging (MRI), to identify epidermalregion 8. In the example of FIG. 1, electrode array patch 6 is appliedto epidermal region 8 on the back of the neck of the patient 4, which isadjacent the occipital nerve of the patient.

Electrode array patch 6 comprises an array of electrodes 10 formed on acarrier. Electrode array patch 6 may conform to epidermal region 8. Insome embodiments, electrode array patch 6 may comprise a rigid materialpre-formed to the contour of epidermal region 8, e.g., by casting ormolding. In other cases, electrode array patch 6 may comprise a flexiblematerial that is formable to the contour of epidermal region 8, e.g.,much like flex circuitry. Exemplary materials for the carrier includesilicone, polyurethane, polyester, and polyimide.

In some embodiments, electrodes 10 may be formed as electricallyconductive pads that are deposited, printed or etched onto thedielectric carrier, along with conductive traces to couple theelectrodes to a cable 14. Cable 14 couples electrodes 10 to screeningcontroller 12. In some embodiments, electrodes 10 may have peaked,spherical, or contoured surfaces designed to enhance coupling pressureand increase contact area with the patient's skin. Cable 14 may includea separate electrical conductor for each electrode 10 so that theelectrodes can be independently energized to deliver stimulation energy.Electrode array patch 6 may be a single layer or multi-layerconstruction, depending on the density of electrodes 10 and associatedconductive traces.

Electrode array patch 6 may have a length of approximately 15 to 20 cm,and a height of approximately 10 to 15 cm. In an exemplary embodiment,electrode array patch 6 includes approximately 10 to 150, and morepreferably 30 to 100, electrodes 10. Electrodes 10 may be formed ascircular, square or rectangular, electrically conductive pads. Eachelectrode 10 may have a surface area in a range of approximately 0.15 to1.0 cm². Electrodes 10 may be arranged in a linear array ortwo-dimensional array of columns and rows, or in a recurring diagonalpattern. Conductive traces may access electrodes 10 directly on theouter surface of the carrier, or from another layer below the outersurface using conductive vias. In some embodiments, cable 14 may beremovably coupled to a connector carried by electrode array patch 6.

Electrode array patch 6 may be adhesively attached to the neck of thepatient 4. In this case, electrode array patch 6 may include anintegrated adhesive layer. FIG. 2 is a side view of electrode arraypatch 6 shown in FIG. 1. In the example of FIG. 2, electrode array patch6 includes a carrier layer 11, an array of electrodes 10 formed on thecarrier layer, and an adhesive layer 13 on a side of the carrier layeradjacent the electrodes. The adhesive layer 13 may be formulated toincorporate an electrically conductive gel for enhanced electricalcoupling between electrodes 10 and the patient's neck. An appropriaterelease layer (not shown in FIG. 2) may be applied to the adhesive layerupon manufacture to permit storage of the electrode array patch.

As an alternative, electrode array patch may be held in place by straps,sutures, adhesive tape, surgical adhesives, or the like. As a furtheralternative, electrode array patch 6 may form part of a head rest thatsupports the head of patient 4. In this manner, gravity forces thepatient's head into contact with electrodes 10 on electrode array patch6. Filling the carrier layer or an adjacent layer with a gel-likematerial may further support conformity of electrode array patch 6 tothe head of patient 4.

Electrode array patch 6 positions electrodes 10 adjacent epidermalregion 8 of patient 4 to apply transcutaneous electricalneurostimulation, sometimes referred to as “TENS,” to the neuralgicregion of patient 4. In other embodiments, the screening device mayutilize another non-invasive way to introduce energy to a patientinstead of TENS. Examples include sonic diathermy, radio frequency (RF)diathermy, standard heating, and standard cooling. Patient response toapplication of stimulation in any of these diverse forms may be helpfulin identifying a stimulation site for neurostimulation.

Each of electrodes 10 may be controlled to deliver stimulationindependently or simultaneously with other electrodes as a group, e.g.,in a unipolar or bipolar configuration. Electrodes 10 may be arranged ina grid pattern, as illustrated in FIG. 1. In other embodiments,electrodes 10 may be arranged in other patterns associated with aspecific neuralgic region. Electrodes 10 on electrode array patch 6 arepositioned adjacent epidermal region 8 of patient 4.

Screening controller 12 permits a caregiver to selectively activatedifferent electrodes 10, or combinations of electrodes, and thereby movean electrical stimulation pattern across electrode array patch 6. Inthis manner, the electrical stimulation pattern can be adjusted toaccess different potential stimulation regions and evaluate the efficacyof neurostimulation at those sites. In some embodiments, one of theelectrodes 10 may serve as a reference electrode for individualelectrodes selected by screening controller 12, providing a unipolararrangement. The reference electrode may be placed on a skin surface ofthe patient or included in the array of electrodes 10 on the electrodearray patch 6. The reference electrode is preferably at least twocentimeters away from the other electrodes 10 to produce a far fieldeffect for unipolar arrangements. Alternatively, screening controller 12may select bipolar pairs of electrodes.

A caregiver operates screening controller 12 to select one or morestimulation regions within epidermal region 8 that substantiallyalleviate the pain experienced by patient 4. Screening controller 12 mayinclude a joystick to move the stimulation up, down, left, or rightacross electrode array patch 6, as will be described with reference toFIG. 3. In other embodiments, controller 12 may comprise arrow keys orthe like to manually position the stimulation. In some cases, screeningcontroller 12 may comprise a computing device that automatically movesthe stimulation across electrode array patch 6.

As the electrical stimulation pattern moves across different electrodecombinations within electrode array patch 6, the caregiver collectsfeedback from patient 4 regarding the effects of the stimulation inrelieving the patient's pain symptoms. The caregiver may record thefeedback within screening controller 12 using an input device such as akeyboard or keypad, or manually record the feedback. In either case, thefeedback is associated with the particular electrode combinationselected at the time the feedback is elicited.

The feedback may comprise an assessment of the amount of painexperienced by the patient during the stimulation. The feedback may beprovided on any of a variety of efficacy rating scales, includingnumeric and qualitative pain scales, or combinations of such scales. Oneexample of a pain rating scale is the visual analog scale. Efficacyfeedback also may include feedback concerning undesirable side effectssuch as pain due to high current density, unwanted parasthesia referenceto other parts of the body, or dizziness. In some cases, the patient maybe permitted to record the feedback directly in screening controller 12,e.g., via a keyboard. For example, patient 4 may provide the feedback toscreening controller 12 directly via an input device such as a button ora keypad. In other embodiments, the caregiver may enter the feedbackfrom the patient to screening controller 12.

In operation, screening controller 12 stimulates one or more electrodes10 corresponding to a first stimulation region within epidermal region 8and receives feedback from the patient regarding the stimulation region.Screening controller 12 then drives one or more electrodes 10 to deliverstimulation energy within a second stimulation region within epidermalregion 8 and receives feedback from the patient regarding the secondstimulation site. The second stimulation region may be located adjacentthe first stimulation region within epidermal region 8. In some cases,the second stimulation region may overlap the first stimulation region.

The electrode selection process may be automated, in some embodiments,to systematically step through adjacent electrode combinations situatedacross electrode array patch 6. The selection process may be designed tofocus on electrode combinations adjacent a given region once efficaciousresults are achieved using other electrode combinations in that region.For example, screening controller 12 may automatically select electrodecombinations using electrodes 10 that “orbit” about an electrode orelectrode combination found to provide good results, before moving on toother regions of electrode array patch 6.

Alternatively, the caregiver may manually operate screening controller12 to move the stimulation pattern in response to the feedback frompatient 4. For example, when the feedback regarding a first stimulationregion indicates at least partial pain alleviation, the caregiver maymanipulate screening controller 12 to define several stimulation regionsthat overlap the first stimulation region. However, when the feedbackregarding the second stimulation region indicates no or insufficientpain alleviation, the caregiver may manipulate screening controller 12to define the next stimulation regions adjacent the first stimulationregion.

As mentioned above, screening controller 12 may be configured to recordefficacy results based on feedback from the patient. Alternatively, inother embodiments, screening controller 12 may simply include an inputmedia, such as a key or button, to permit the caregiver to markelectrode combinations, and stimulation regions, found to provideespecially good alleviation of the patient's symptoms. In either cases,screening controller 12 stores the marked stimulation regions, andoptionally the feedback associated with such sites.

Once the transcutaneous stimulation screening is complete, the caregiverselects a stimulation region from the marked stimulation regions basedon the feedback and an implantation risk identified for each of themarked stimulation regions. The transcutaneous stimulation screening maybe complete when the electrical stimulation pattern has moved across theentire electrode array patch 6, or the caregiver has otherwiseterminated the screening. In some embodiments, screening controller 12may automatically select a stimulation region for recommendation to thecaregiver, e.g., based on relative feedback regarding efficacy of thevarious stimulation regions.

FIG. 3 is a schematic diagram illustrating one example of an inputdevice 16 that may form part of screening controller 12 of FIG. 1. Asshown in FIG. 3, input device 16 may take the form of a joystick with anactuator stick 17 to select electrode combinations and an input button18 to activate delivery of transcutaneous neurostimulation. Input device16 is used to move electrical stimulation across electrode array patch 6by selection of different combinations of electrodes 10. A firstdepression of button 18 may be used to trigger delivery of stimulationenergy, while a second depression of button 18 terminates delivery ofstimulation energy. In addition, a second button 19 can be provided tomark electrode combinations within epidermal region 8 that appear tosupport efficacy based on feedback from the patient 4. The markedelectrode combinations may be recorded by screening controller 12 inresponse to depression of button 19.

In operation, screening controller 12 drives one or more electrodes 10that correspond to a first stimulation region. The caregiver thenmanipulates input device 16 to move the stimulation up, down, left, orright across electrode array patch 6 to one or more electrodes 10 thatcorrespond to a second stimulation region. In some cases, thestimulation may be moved diagonally across electrode array patch 6. Theposition of the stimulation pattern may be presented graphically on adisplay device, or by textual information on a display device such asnumbers or letters corresponding to electrode combinations.

The caregiver may use input device 16 to move the stimulation inresponse to feedback from patient 4. For example, when the feedbackregarding the first stimulation region indicates at least partial painalleviation, the physician or clinician may manipulate input device 16to manually position the second stimulation region in a positionoverlapping the first stimulation region. Again, positioning may beconfirmed by a display device that presents selected electrodecombinations, location information, or both. However, when the feedbackregarding the first stimulation region indicates no pain alleviation,the caregiver may manipulate input device 16 to manually position thesecond stimulation at a site adjacent the first stimulation region.Alternatively, as mentioned above, screening controller 12 may beconfigured to automatically select electrode combinations. Screeningcontroller 12 may permit the caregiver to select either a manualselection mode using input device 16 or an automatic selection mode.

Also, as mentioned above, the caregiver may depress button 19 to mark astimulation region when the feedback regarding the stimulation regionindicates effective pain alleviation. In other embodiments, input device16 may include additional buttons or a keypad for patient 4, thecaregiver, or both to input feedback to controller 12. Controller 12 maystore the marked stimulation regions and the corresponding feedback.Once the transcutaneous stimulation screening is complete, the physicianor the clinician may select a stimulation region from the markedstimulation regions based on the feedback. In some embodiments,screening controller 12 may select the stimulation region from themarked stimulation regions.

FIG. 4 is a block diagram illustrating screening controller 12 of FIG. 1in greater detail. As shown in FIG. 4, screening controller 12 includesa processor 21, a pulse generator 23, switch matrix 25, and a userinterface 27. Processor 21 controls pulse generator 23 and switch matrix25 in response to input from input device 16. In particular, processor21 activates pulse generator 23 to generate neurostimulation pulses forapplication across a set of two or more electrodes. Processor 21 mayspecify parameters such as amplitude, frequency, pulse width andduration for the neurostimulation pulses based on a prestoredneurostimulation program, or adjust such parameters in response to inputfrom the caregiver.

As an example, for transcutaneous stimulation to identify a stimulationregion, processor 21 may control pulse generator 23 to generate astimulation waveform having an amplitude of approximately 10 to 100milliamps, a frequency of approximately 10 to 500 Hz, and morepreferably 20 to 200 Hz, a pulse width of approximately 20 to 800microseconds, and more preferably 80 to 120 microseconds, and a durationof approximately a few seconds to several minutes. The stimulation pulsefor transcutaneous stimulation may have a substantially square or spikedwaveform. A stimulation waveform having the above parameters should beeffective in evaluating efficacy of different stimulation regions.However, screening controller 12 may permit the caregiver to makefurther adjustments to the stimulation waveform, if desired.

Processor 21 also controls switch matrix 25 to couple selectedelectrodes 10 to pulse generator 23. As an example, switch matrix 25 maybe an array of solid state switches that can be controlled by a codewordgenerated by processor 21 to couple selected electrodes to pulsegenerator 23. As the caregiver manipulates input device 16 to activatestimulation and move to different electrode combinations, processor 21controls pulse generator 23 and switch matrix 25 in a correspondingmanner.

User interface 27 includes input device 16 and an output device 29.Input device 16 may include a joystick device, as in FIG. 3, as well asother input media to permit a caregiver or patient to enter informationincluding stimulation commands, efficacy feedback, and the like. Outputdevice 29 may include a display device to present operational and statusinformation during the course of a screening session, and to indicatethe position of a particular electrode combination under evaluation. Inparticular, output device 29 may track the movement of the appliedstimulation pattern as a function of joystick movement.

FIG. 5 is a schematic diagram illustrating an example of a percutaneousmicro-electrode needle array screening device 20. Upon selection of anefficacious stimulation region using transcutaneous stimulationscreening system 2 (FIG. 1), additional screening techniques can beapplied to identify a stimulation site within the selected stimulationregion with greater precision. As an example, percutaneousmicro-electrode needle array screening device 20 is placed over thestimulation region identified by transcutaneous screening, and thenforced into the tissue at the stimulation region such that an array ofneedle electrodes 22 penetrates the skin and protrudes into the tissuein the epidermal region.

As shown in FIG. 5, device 20 may include a disc-like base 24 supportingthe array of needle electrodes 22. A conductor network within base 24provides multiple, independent electrical conductors. Each conductor iscoupled to one of needle electrodes 22 and extends away from base 24within cable 37. Cable 37 may be connected to screening controller 12 ofFIGS. 1, 3 and 4 to couple the individual needle electrodes 22 to switcharray 25 and pulse generator 23. In this manner, the needle electrodes22 receive stimulation energy for percutaneous application tostimulation sites within the stimulation region in the neck of patient4.

The micro-electrode needle array screening device 20 further localizesthe stimulation region selected by the transcutaneous stimulationscreening device 2 (FIG. 1) to select a more specific stimulation siteat which to chronically implant a neurostimulator for treatment of theneuralgic region of patient 4. If the chronic neurostimulator has anarray of electrodes, the localized stimulation site also may permit acaregiver to select an initial combination of electrodes that arepositioned to target the stimulation site. Needle electrodes 22 aresized and constructed to permit a caregiver to insert the needles intoepidermal region 8. As an example, each needle electrode 22 may have asharp pointed distal tip, an outer diameter of approximately 250 to 1000microns, and a length of approximately 5 to 30 mm. Disc-like base 24 mayhave a diameter of approximately 1 to 5 cm, and a surface area ofapproximately 70 to 2000 mm². However, disc-like base 24 need not becircular. Needle electrodes 22 may be distributed across the entiresurface of disc-like base 24.

Needle electrodes 22 are constructed from a biocompatible, electricallyconductive metal, such as MP (nickel-cobalt) alloy, platinum, stainlesssteel, or tungsten. However, each needle electrode 22 may be insulatedby an outer sheath that extends along substantially the entire length ofthe needle electrode, leaving a distal tip exposed for delivery ofstimulation energy. In this manner, the depth at which the stimulationenergy is actually delivered can be controlled by selecting differentneedle lengths or different outer sheath lengths.

Screening controller 12 is used to move the electrical stimulationacross micro-electrode needle array 20. In particular, screeningcontroller 12 selects combinations of two or more electrode needles fordelivery of neurostimulation energy. The location of each stimulationsite may be presented graphically or textually as the screening processprogresses. The parameters for percutaneous delivery of neurostimulationenergy may be different than for transcutaneous delivery. For example,the neurostimulation waveform generated by pulse generator 23 forpercutaneous stimulation may have an amplitude of approximately 1 to 40milliamps, and more preferably 6 to 10 milliamps, a frequency ofapproximately 10 to 500 Hz, and more preferably 20 to 200 Hz, a pulsewidth of approximately 20 to 800 microseconds, and more preferably 80 to120 microseconds, and a duration of approximately a few seconds toseveral minutes. The stimulation pulse for transcutaneous stimulationmay have a substantially square or spiked waveform.

As in the case of transcutaneous screening stimulation, the caregiveroperates screening controller 12 to localize the selected stimulationregion based on the efficacy of the percutaneous stimulation. Forexample, the caregiver may adjust an input device 16 (FIG. 3) tomanually position the stimulation at a selected stimulation site withinthe stimulation region. Alternatively, screening controller 12 mayselect different unipolar or bipolar electrode combinations on anautomated basis. As the electrical stimulation moves acrossmicro-electrode needle array 20, the caregiver or screening controller12 receives feedback from patient 4 regarding the efficacy of thestimulation in relieving pain symptoms.

In operation, the percutaneous micro-electrode needle array screeningdevice 20 is used to apply neurostimulation energy to a firststimulation site within epidermal region 8 of patient 4. Screeningcontroller 12 applies stimulation energy via one or more electrodescorresponding to several stimulation sites at the first stimulationsite. Screening controller 12 then receives feedback from the patient 4or the caregiver regarding the efficacy of neurostimulation energydelivered via the selected stimulation site. This process continuesuntil all electrode combinations have been evaluated, or the caregiverterminates the process. Once the stimulation screening is complete, thecaregiver may select the best stimulation site based on the feedback andthe identified implantation risk for the specific stimulation site. Insome embodiments, controller 12 may automatically select the stimulationsite, e.g., based on an efficacy rating, and provide a recommendation tothe caregiver.

FIG. 6 is a schematic diagram illustrating a temporary subcutaneousscreening device 26. Temporary subcutaneous implantable screening device26 is subcutaneously implanted in patient 4 at a stimulation siteselected by either the transcutaneous stimulation screening device fromFIG. 1 or the percutaneous micro-electrode screening device from FIG. 5.Temporary subcutaneous screening device 26 provides temporary electricalstimulation to the neuralgic region of patient 4 to further evaluate theefficacy of the selected stimulation site.

As shown in FIG. 6, temporary subcutaneous implantable screening device26 includes a housing 31 that carries electrodes 28A-28B (collectively“electrodes 28”), control circuitry 30, and a battery 32. For ease ofillustration, electrical conductors coupling electrodes 28, circuitry30, and battery 32, are not shown in FIG. 6. Housing 31 conforms to aminiaturized form factor that allows subcutaneous implantation oftemporary implantable screening device 26 at the stimulation site in theback of the neck of patient 4 adjacent the occipital nerve. Housing 31may have a potted casing that encapsulates the components.

Circuitry 30 couples to electrodes 28 and battery 32. Battery 32 may bea lithium ion battery. Battery 32 may comprise a pin cell battery or aflat button cell battery. Circuitry 30 includes a pulse generator togenerate a neurostimulation waveform for application via electrodes 28A,28B. Battery 32 provides power to circuitry 30 to generated stimulationenergy for electrodes 28 on a temporary basis. Electrodes 28 may beformed on housing 31 as end-cap electrodes or ring electrodes. Battery32 may have a lifetime of at least one day. In the case of a pin cell,battery 32 preferably has a compression fit feedthrough pin, such as ariveted or crimped feedthrough, and an aluminum case to permit a thinprofile. With temporary subcutaneous stimulation device 26, patient 4can determine whether the selected stimulation site allows substantialpain alleviation before chronic implantation of a neurostimulator.

Temporary subcutaneous screening device 26 also includes a removal loop33 partially encapsulated in housing 31. Removal loop 33 defines a hole35 that allows easy explantation of subcutaneous screening device 26from the selected stimulation site using a hook that extends into hole35. Accordingly, the caregiver may use a tool with a hook sized toengage with removal loop 33 to pull subcutaneous screening device 26 outof patient 4 when battery 32 runs out of power.

For purposes of temporary screening, circuitry 30 need not be adjustablenor include telemetry electronics. Instead, circuitry 30 may beconfigured to generate a fixed neurostimulation waveform. Forsubcutaneous application, the fixed neurostimulation waveform may have afixed amplitude of approximately 1 to 40 milliamps, and more preferably6 to 10 milliamps, a fixed frequency of approximately 10 to 800 Hz, andpreferably 40 to 60 Hz, a fixed pulse width of approximately 20 to 800microseconds, and more preferably 80 to 120 microseconds, and a fixedduty cycle in a range of approximately 15 to 25 percent, i.e., “on” for15 to 25 percent of the time, and more preferably 20 percent of thetime.

Subcutaneous screening device 26 may be sized for implantation under aflap of skin in the back of the neck of patient 4. In particular,subcutaneous screening device 26 may have a cylindrical capsule-likeshape or generally flat rectangular shape. For a generally flatrectangular shape, device 26 may have a length of approximately 30 to 50mm, a width of approximately 10 to 20 mm, and a thickness ofapproximately 3 to 6 mm. For a capsule shape, device 26 may have alength of approximately 30 to 50 mm, and a diameter of approximately 3to 6 cm. As shown in FIG. 6, subcutaneous screening device 26 may havegenerally atraumatic rounded-ends to promote subcutaneous implantationwithout substantial discomfort to patient 4. In some embodiments,instead of implantation under a flap of skin, subcutaneous screeningdevice 26 may be introduced via a percutaneous injection needle. As afurther alternative, instead of a capsule-like housing, subcutaneousscreening device 26 may have a flat or angled housing as described belowwith reference to the chronically implantable neurostimulator of FIGS.7-18.

FIG. 7 is a schematic diagram illustrating an example neurostimulator 34for chronic subcutaneous implantation in an occipital nerve region atthe back of a neck of a patient 4. Once a viable stimulation site isselected based on transcutaneous trial stimulation, percutaneous trialstimulation, and temporary subcutaneous trial stimulation, aneurostimulator 34 can be chronically implanted to provide on-sitetreatment of neuralgia experienced by patient 4. Neurostimulator 34 maybe implanted at a stimulation site tested by temporary subcutaneousscreening device 26 from FIG. 6. The caregiver may elect tosubcutaneously implant neurostimulator 34 at the stimulation site whenthe temporary implantable screening device is found to substantiallyalleviates pain symptoms experienced by patient 4. In addition, in theevent the neurostimulator 34 has an array of electrodes, the caregivermay program the neurostimulator to deliver stimulation via a selectedcombination of electrodes that are best positioned to target thestimulation site.

Neurostimulator 34 has a miniaturized form factor and a low profile thatpermits subcutaneous implantation at the selected stimulation sitedirectly adjacent the neuralgic region of patient 4. For example,neurostimulator 34 may be implanted under a flap of skin at the back ofthe neck. Neurostimulator 34 may be generally thin and flat and, in someembodiments, may be angled or curved to better conform to the curvatureat the back of the patient's neck. In particular, neurostimulator 34 mayhave a degree of curvature selected to conform to a radius of thestimulation site. For example, the degree of curvature may beapproximately 20 to 40 degrees, and more preferably approximately 30degrees. With this radius of curvature, and a very thin housing,neurostimulator 34 exhibits a low profile and may be barely noticeableto patient 4 and others.

Neurostimulator 34 includes a battery, control circuitry, one or moreelectrodes to provide stimulation to the neuralgic region of patient 4,and wireless telemetry circuitry to communicate with an externalprogrammer to permit adjustments to neurostimulation therapy orinterrogation of the operational status of the neurostimulator. Thebattery within neurostimulator 34 may be rechargeable, and may have acapacity of at least 20 milliamp-hr. The control circuitry may includean application specific integrated circuit (ASIC) designed to minimizethe number of components within the housing of neurostimulator 34. Theelectrodes may comprise an array of electrodes that provides thecaregiver with enhanced programming flexibility. In particular, acaregiver may program neurostimulator 34, via wireless telemetry, toselect particular electrodes for delivery of neurostimulation. In somecases, the array of electrodes may be integrated with the housing ofneurostimulator 34 on a side adjacent the neuralgic region of patient 4.Various embodiments of neurostimulator 34 will be described in greaterdetail below.

FIG. 8 is a flow chart illustrating a multi-step screening process toselect a stimulation site for treatment of the neuralgic region ofpatient 4. In general, the multi-step screening process may include afirst step involving application of electrode array patch 6 fortranscutaneous stimulation, a second step involving application of amicro-electrode needle array 20 for percutaneous stimulation, a thirdstep involving temporary implantation of a subcutaneous trial stimulator26, and a fourth step of chronic implantation of a subcutaneousstimulator 34. In the second step, the location of an efficaciousstimulation region is further refined in order to select a stimulationsite for temporary and chronic implantation. Although four steps aredescribed, a lesser number of steps may be used in some embodiments. Forexample, one or more of the transcutaneous, percutaneous, or temporarysubcutaneous steps may be omitted, although all of the steps may bedesired in some embodiments.

As shown in FIG. 8, a caregiver, such as a physician or clinician, firstmay perform imaging, such as MRI, to identify epidermal region 8 ofpatient 4 adjacent the neuralgic region (36). Using the imaging results,the caregiver visualizes a target stimulation region. The caregiver thenapplies an electrode array patch 6 to the target stimulation region ofpatient 4, and activates screening controller 12 to apply transcutaneousstimulation. Based on feedback from the patient 4, the caregiverevaluates different electrode combinations to non-invasively select afirst stimulation region that appears to provide relief for symptomssuffered by the patient (38). Screening controller 12 drives electrodes10 on electrode array patch 6 to transcutaneously deliverneurostimulation energy in other stimulation regions.

Upon selection of a stimulation region, the caregiver appliesmicro-electrode needle array 20 in the vicinity of the stimulationregion. In particular, the caregiver forces micro-electrode needle array20 against the patient's neck so that needle electrodes 22 penetrateinto tissue at the first stimulation region. The caregiver then usesscreening controller 12 to apply stimulation via different combinationsof percutaneous needle electrodes 22. By selecting differentcombinations of needle electrodes 22, and receiving feedback, thecaregiver selects a stimulation site (40). The stimulation site iswithin the stimulation region defined by transcutaneous screening, andserves to further refine the location for delivery of stimulation.Screening controller 12 drives micro-electrode needle electrodes 22 onmicro-electrode array 20 and may receive feedback from patient 4regarding efficacy of stimulation. The caregiver selects the stimulationsite within the stimulation region based on the feedback. In this way,the micro-electrode screening device further localizes the stimulationregion for chronic implantation of neurostimulator 34.

Upon identification of the stimulation site, and prior to chronicimplantation, the caregiver may subcutaneously implant a temporaryimplantable screening device 26 at the stimulation site to furtherevaluate the efficacy of the stimulation site (42). Temporary screeningdevice 26 delivers stimulation energy subcutaneously. If the temporaryscreening device 26 is effective, the caregiver may then elect tochronically implant neurostimulator 34 at the stimulation site. Iftemporary implantable screening device 26 does not substantiallyalleviate pain at the neuralgic region (no branch of 44), however, thecaregiver may select another stimulation site within the firststimulation region with the micro-electrode needle screening device(40). Temporary implantable screening device 26 is used to test thenewly selected stimulation site for efficacy. If temporary implantablescreening device 26 substantially alleviates pain at the neuralgicregion (yes branch of 44), the physician chronically implants asubcutaneous neurostimulator 34 at the stimulation site (46).

FIGS. 9A-18 illustrate various embodiments of a chronically implantedsubcutaneous neurostimulator. Some of the structural and functionalaspects depicted in FIGS. 9A-18 also may be used for a temporarysubcutaneous neurostimulator. FIG. 9A illustrates a top view of aneurostimulator 50 for chronic subcutaneous implantation. FIG. 9Billustrates a side view of neurostimulator 50. Neurostimulator 50 isdesigned to deliver on-site neurostimulation for treatment of neuralgiaexperienced by a patient. Neurostimulator 50 may be subcutaneouslyimplanted at a stimulation site adjacent a neuralgic region of thepatient. For example, neurostimulator 50 may be subcutaneously implantedat the back of the neck of the patient to relieve occipital neuralgia, amigraine-like pain originating along the occipital nerve. As describedabove, a caregiver may select the stimulation site based on feedbackfrom the patient to one or more of a transcutaneous stimulationscreening device, a percutaneous micro-electrode needle array screeningdevice, and a temporary subcutaneous implantable screening device.

As shown in FIGS. 9A and 9B, neurostimulator 50 comprises a housing 51that houses a control module 52, a battery 54, and a coil 56 encirclingcontrol module 52. Coil 56 may serve as an inductive power interface torecharge battery 54, as well as a telemetry coil for wirelesscommunication with an external programmer. In some embodiments, coil 56may encircle control module 52, battery 54, or both. Coil 56 inductivelyreceives energy from an external recharging unit (not illustrated)through the skin of the patient to recharge battery 54. Coil 56 may beformed of windings of copper or another highly conductive material.

Neurostimulator 50 also includes two or more electrodes 53, 55 toprovide stimulation to the neuralgic region of the patient. Controlmodule 52 receives power from battery 54 to drive the electrodes 53, 55according to a stimulation program included in control module 52. Theelectrodes 53, 55 may comprise a pair of electrodes or an array ofelectrodes, illustrated in FIGS. 10-12. An array of electrodes providesenhanced stimulation programming flexibility. In some cases, the arrayof electrodes may be integrated on housing 51 of neurostimulator 50, asshown in FIG. 9B.

As shown in FIG. 9A, housing 51 conforms to a substantially rectangularform factor. In this case, housing 51 may include the array ofelectrodes on a side of housing 51 positioned adjacent the neuralgicregion. In other cases, the housing may conform to a substantiallycylindrical form factor, illustrated in FIGS. 16-18, and include ringelectrodes along a length of the housing.

Housing 51 may conform to a miniaturized form factor with a low profilein order to fit directly adjacent the neuralgic region of the patient.As illustrated in FIG. 9B, housing 51 may also comprise a degree ofcurvature to conform to a radius of the stimulation site. Housing 51 maybe pre-formed with a degree of curvature. In other cases, the physicianmay bend housing 51 to a degree of curvature appropriate for a specificstimulation site. For example, housing 51 may comprise a flexiblematerial or include bellows that allow housing 51 to bend. In eithercases, housing 51 may be angled, curved or jointed to better accommodatethe curvature at the back of the patient's neck.

In the example of FIGS. 9A and 9B, housing 51 has a joint 57 between theportion of the housing containing control module 52 and the portioncontaining battery 54. FIG. 9B, in particular, illustrates a desiredradius of curvature that permits housing 51 to better conform to thegeometry of the implant site at the back of the patient's neck. Theradius of curvature may be expressed as an angle A defined between aline tangent to the apex of joint 57 and a line within either of the twomajor planes defined by housing 51, i.e., on either side of joint 57. Asdiscussed previously, the angle A representing the desired radius ofcurvature may be approximately 20 to 40 degrees, and more preferablyapproximately 30 degrees.

Housing 51 may also define apertures 58A and 58B (collectively“apertures 58”). Apertures 58 may operate as both suture and removalholes. The physician may anchor neurostimulator 50 at the stimulationsite adjacent the neuralgic region of the patient by suturing housing 51to surrounding tissue via apertures 58. In order to removeneurostimulator 50 from the stimulation site, the physician may cut thesutures and then use a tool, e.g., a hook, that engages with at leastone of apertures 58 to easily pull neurostimulator 50 out of theimplantation site.

Battery 54 may comprise a rechargeable battery with a capacity of atleast 20 milliamp-hr, more preferably at least 25 milliamp-hr, and stillmore preferably at least 30 milliamp-hours. In this case, battery 54comprises a capacity almost an order of magnitude larger thanconventional microstimulators. In some embodiments, battery 54 maycomprise a lithium ion rechargeable battery. Control module 52 alsocouples to coil 56, which may operate as both a recharge coil and atelemetry coil. Control module 52 receives energy via recharge coil 56to recharge battery 54. Control module 52 may also transmit or receivestimulation programming commands, instructions, or other instructionsvia telemetry coil 56.

Control module 52 may comprise an ASIC designed to minimize the numberof components within neurostimulator 50. The ASIC may be designed withan IC using the 0.8 micron process in an effort to reduce the overallsize and profile of neurostimulator 50. The ASIC may include both abattery recharge module and a telemetry module that couple to coil 56,as well as a pulse generator and processor. The processor directs thepulse generator to drive one or more electrodes based on stimulationprograms stored in memory accessible by the control module 52 orreceived by the telemetry module. A power management module coupled tobattery 54 powers the control circuitry within control module 52.

Housing 51 may be formed from any of a variety of materials such assilicone, polyurethane, other polymeric materials, titanium, stainlesssteel or ceramics. In some embodiments, as will be described, housing 51may be generally soft and flexible, and may include a flexible memberthat at least partially encapsulates the battery 54, control module 52and coil 56. In some embodiments, the flexible member may be an overmoldthat is molded about all or some of control module 52, battery 54 andcoil 56. Control module 52 and coil 56 are designed to be very thin andflat to permit subcutaneous implantation. Similarly, battery 54 may be alithium ion battery with a thin, generally flat housing or cylindricalhousing. In the case of a pin type cell, battery 54 may have an aluminumhousing with a crimped or riveted pin feedthrough. In some embodiments,battery 54 alternatively may comprise a foil pack battery. In anexemplary embodiment, neurostimulator 50 may have a length ofapproximately 30 to 50 mm, a width of approximately 10 to 20 mm and athickness of approximately 3 to 6 mm.

Each of electrodes 53, 55 may be circular, square or rectangular. In thecase of a circular shape, each electrode, may have a diameter ofapproximately 0.5 to 1.5 mm, and more preferably 1 mm. Although twoelectrodes 53, 55 are shown in FIGS. 9A and 9B, a larger number ofelectrodes may be provided in a linear or two-dimensional array. Forexample, neurostimulator 50 may include between approximately 2 and 32electrodes, distributed in a linear or two-dimensional array. A lineararray generally refers to an ordering of electrodes along a common line,whereas a two-dimensional array generally refers to an ordering ofelectrodes along at least two different lines, e.g., as rows andcolumns. In either case, the array of electrodes may have a regular,periodic pattern such that electrodes are positioned at regular spatialintervals within a line, row or column. Alternatively, the array may beirregular such that electrodes are positioned at irregular intervals orat positions that do not represented an ordered pattern.

FIG. 10 is a schematic diagram illustrating a bottom view of aneurostimulator 50A in accordance with an alternative embodiment of theinvention. FIG. 11 is an exemplary side view of the neurostimulator ofFIG. 10. Neurostimulator 50A comprises a housing 51A and apertures 58.Neurostimulator 50A may be substantially similar to neurostimulator 50of FIGS. 9A and 9B. However, neurostimulator 50A includes atwo-dimensional array of electrodes 60 integrated on housing 51A. Inother embodiments, a linear array of electrodes 60 may be provided.

Each of electrodes 60 may be coupled to control module 52 within housing51A. A combination of electrodes 60, such as a bipolar electrode pair,may be selected based on the position of the electrodes relative thestimulation site identified in the screening process. For example,neurostimulator 50 may be initially programmed to deliver stimulationenergy via a combination of electrodes that are positioned closest tothe identified stimulation site. Alternatively, a unipolar arrangementmay be selected.

Neurostimulator 50A may have a joint 57, as in FIGS. 8 and 9, betweenthe portion of the housing containing a control module and the portioncontaining a battery, thereby promoting conformance to the back of theneck of a patient. The caregiver may implant neurostimulator 50A at theselected stimulation site with the array of electrodes 60 directlyadjacent the neuralgic region of the patient. The array of electrodes 60allows the caregiver flexibility in programming the stimulation patternprovided by neurostimulator 50A.

Like housing 51 in FIGS. 9A and 9B, housing 51A of FIG. 10 may have asubstantially miniaturized form factor and a low profile to fit withinthe stimulation site. A control module within neurostimulator 50A can beprogrammed to apply selected combinations of the electrodes 60 toachieve desired efficacy. In particular, at the time of implantation, acaregiver may test different electrode combinations and programneurostimulator 50A to apply a selected combination. Again, theprogramming may take place by wireless telemetry via a coil carried byneurostimulator 50A.

FIG. 12 is a schematic diagram illustrating another exemplary bottomview of a neurostimulator 50B in accordance with an embodiment of theinvention. Neurostimulator 50B comprises a housing 51B and apertures 58.Neurostimulator 50B maybe substantially similar to neurostimulator 50from FIGS. 9A and 9B. However, neurostimulator 50B includes a flexiblemember 62, such as an overmold, that encapsulates housing 51B. In somecases, flexible member 62 may only partially encapsulate housing 51B.Neurostimulator 50B also includes an array of electrodes 63 integratedon flexible member 62 at opposing ends of housing 51B. Each ofelectrodes 63 may couple to control module 52 within housing 51B. Atleast a portion of each electrode 63 protrudes through flexible member62 for contact with tissue within patient 4.

The physician may implant neurostimulator 50B at the selectedstimulation site with the array of electrodes 63 adjacent the neuralgicregion of the patient. Flexible member 62 may comprise a substantiallyflexible polymer with tapered edges. In this way, flexible member 62allows more flexibility in the placement of electrodes 63 thanintegrating the electrodes into the housing, as illustrated in FIG. 10.Furthermore, flexible member 62 may smooth the transition from housing51B to the tissue surrounding neurostimulator 50B. Althoughneurostimulator 50B has a larger volume than a neurostimulator without aflexible member, e.g., neurostimulator 50A, flexible member 62 mayimprove cosmesis and prevent erosion of the epidermal region adjacentthe stimulation site.

FIG. 13 is a schematic diagram illustrating another exemplary bottomview of a neurostimulator 50C in accordance with an embodiment of theinvention. Neurostimulator 50C comprises a housing 51C and apertures 58.Neurostimulator 50C is substantially similar to neurostimulator 50 fromFIGS. 9A and 9B. However, neurostimulator 50C further includes anelectrode array 64 tethered to housing 51C, via a cable 61. Electrodearray 64 includes an array of electrodes 65. In some cases, electrodearray 64 comprises a flexible polymer and electrodes 65 may be potted inelectrode array 64. Each of electrodes 65 may couple to control module52 within housing 51C via conductors within cable 61.

The physician may implant neurostimulator 50C at the selectedstimulation site with the tethered array of electrodes 65 adjacent theneuralgic region of the patient. Tethered electrode array 64 allows moreflexibility in the placement of electrodes 64. However, neurostimulator50C may have a larger overall implantation volume than a neurostimulatorwith electrodes integrated on a housing, e.g., neurostimulator 50A, oron a flexible member, e.g., neurostimulator 50B.

In some cases, electrode array 64 may comprise a thinner profile thanneurostimulator 50C such that electrode array 64 may be positioneddirectly at the stimulation site and neurostimulator 50C may bepositioned near the stimulation site at a more desirable implantationsite. In this way, neurostimulator 50C may improve cosmesis and preventerosion of the epidermal region adjacent the stimulation site.

FIG. 14 is a schematic diagram illustrating an exemplary tool 66 forinsertion or removal of a neurostimulator. The physician may use tool 66when implanting or explanting neurostimulator 50 from FIGS. 9A and 9B.Tool 66 comprises a base 67, a shaft 68, and a hook 69. The physicianmay subcutaneously implant neurostimulator 50 by engaging hook 69 withone of apertures 58 of neurostimulator 50 and feeding neurostimulator 50into the stimulation site with shaft 68. The physician may grip base 67to manipulate neurostimulator 50 into the proper position. The physicianmay explant neurostimulator 50 from the stimulation site bysubcutaneously inserting shaft 68 at the stimulation site and engaginghook 69 with one of apertures 58 of neurostimulator 50. The physicianthen grips base 67 and pulls neurostimulator 50 out of the stimulationsite. In some cases, shaft 68 may comprise an adjustable length to allowthe physician to reach a variety of stimulation sites without requiringdifferent tools.

FIG. 15A illustrates a top view of another neurostimulator 70. FIG. 15Billustrates a side view of neurostimulator 70. Neurostimulator 70 may besubstantially similar to neurostimulator 50 from FIGS. 9A and 9B. Forexample, neurostimulator 70 may be subcutaneously implanted at astimulation site adjacent a neuralgic region of a patient. Inparticular, neurostimulator 70 may be subcutaneously implanted at theback of the neck of the patient to relieve occipital neuralgia. However,housing 71 may have a substantially rectangular form factor.

As shown in FIGS. 15A and 15B, neurostimulator 70 comprises a housing 71that houses a control module 72, a battery 74, and a coil 76 encirclingcontrol module 72. Neurostimulator 70 also includes two or moreelectrodes 77, 79 to provide stimulation to the neuralgic region of thepatient. Control module 72 receives power from battery 74 to drive theelectrodes according to a stimulation program included in control module72. The electrodes 77, 79 alternatively may comprise a linear ortwo-dimensional array of electrodes substantially similar to theexamples of neurostimulator 50 illustrated in FIGS. 10-13.

Housing 71 conforms to a substantially rectangular form factor. In thiscase, housing 71 may include the array of electrodes integrated on aside of housing 71 positioned adjacent the neuralgic region. Housing 71conforms to a miniaturized form factor with a low profile in order tofit directly adjacent the neuralgic region of the patient. For example,housing 71 may have a length L less than approximately 50 mm, a width ofless than approximately 20 mm, and a thickness of less thanapproximately 6 mm. In a specific example for the housing 71 illustratedin FIGS. 15A and 15B, housing 71 comprises a length L of less than orequal to 36.6 mm (1.44 inches), and width W of less than or equal to14.5 mm (0.57 inches), and a thickness T of less than or equal to 4.5 mm(0.177 inches). In some embodiments, housing 71 may includeapproximately 0.25 mm (0.01 inches) of insulation between control module72 and battery 74 and housing 71. The walls of housing 71 may comprise atotal thickness of approximately 0.71 mm (0.03 inches).

Battery 74 may comprise a rechargeable battery with a capacity of atleast 20 milliamp-hours, more preferably at least 25 milliamp-hours, andstill more preferably at least 30 milliamp-hours. In some embodiments,battery 74 may comprise a lithium ion rechargeable battery. Battery 74may conform to a miniaturized form factor to fit within housing 71.Battery 74 may comprise a length of less than or equal to approximately24.9 mm (0.98 inches), a width of less than or equal to approximately12.7 mm (0.50 inches), and a thickness of less than or equal toapproximately 3.3 mm (0.13 inches). Battery 74 may conform to one of avariety of designs. Some examples are given in Table 1 below. TABLE 13.3 mm 3.0 mm thick 3.0 mm thick 3.3 mm thick thick standard adjustablestandard adjustable loading loading loading loading Length (mm) 25.425.4 25.4 24.9 Width (mm) 16.5 14.2 13.2 12.7 Capacity (mA-hr) 30 30 3130 Case volume (cc) 1.26 1.08 1.11 1.04 Coating (mg/cm²) 22 12.1 2212.32

Neurostimulator 70 may be over-discharge protected. However, sincebattery 74 conforms to an extremely small form factor, theover-discharge protection may be difficult to realize using traditionalapproaches, such as extra battery capacity. Therefore, neurostimulator70 may include a switch to disconnect battery 74 from the load when apredetermined voltage is reached. In other cases, battery 74 maycomprise an over-discharge tolerant battery.

Control module 72 may also conform to a miniaturized form factor to fitwithin housing 71. Control module 72 may comprise a length of less thanor equal to approximately 6.5 mm (0.256 inches), a width of less than orequal to approximately 9.4 mm (0.37 inches), and a thickness of lessthan or equal to approximately 3.6 mm (0.14 mm). Control module 72 alsocouples to coil 76 that may operate as both a recharge coil and atelemetry coil. Control module 72 may receive energy via recharge coil76 to recharge battery 74. Control module 72 may also receivestimulation programs and other instructions from the patient, thephysician, or the clinician via telemetry coil 76.

Although battery 74 comprises a capacity almost an order of magnitudelarger than some conventional microstimulators, battery 74 has arelatively small capacity compared to full size neurostimulators.Therefore, coil 76 may comprise a smaller coil than traditionalneurostimulators. Coil 76 comprises inner dimensions slightly largerthan the dimensions of control module 72 given above. Coil 76 maycomprise an inner length of approximately 6.7 mm (0.265 inches) and aninner width of approximately 9.7 mm (0.38 inches). The outer dimensionsof coil 76 may comprise an outer length of approximately 8.4 mm (0.33inches) and an outer width of approximately 11.7 mm (0.46 inches). Coil76 may also comprise a thickness of approximately 2.5 mm (0.10 inches).

Control module 72 comprises an application specific IC 78 designed tominimize the number of components within neurostimulator 70. IC 78 maybe designed using the 0.8 micron process in an effort to reduce theoverall size and profile of neurostimulator 70. With sufficientprocessing power, IC 78 may have a footprint of approximately 5.2 mm(0.204 inches) by 5.2 mm and a thickness of approximately 0.46 mm (0.018inches).

FIG. 16 is a block diagram illustrating an exemplary control module 80included in an on-site neurostimulator for the treatment of neuralgiaexperienced by a patient. Control module 80 may be used to form controlmodule 72 of neurostimulator 70 illustrated in FIGS. 15A and 15B orcontrol module 52 illustrated in FIGS. 9A and 9B. Control module 80comprises an IC 81, stimulation capacitors and inductors 94, filter andtelemetry components 97, and a crystal oscillator 98 positioned on asubstrate board. The substrate board may comprise a minimal number oflayers, e.g. four layers or less, and comprise a thickness equal to orless than approximately 0.4 mm (0.014 inches).

Control module 80 couples to a rechargeable battery 90, conductors 92that connect to one or more stimulation electrodes of theneurostimulator, and a recharge and telemetry coil 96. Rechargeablebattery 90 may have a capacity of at least 20 milliamp-hours, morepreferably at least 25 milliamp-hours, and still more preferably atleast 30 milliamp-hours. In some embodiments, battery 90 may comprise alithium ion rechargeable battery. Coil 96 operates as both a rechargecoil and a telemetry coil. In some cases, as described above, coil 96may encircle control module 80.

IC 81 may be formed as an ASIC designed to minimize the number ofcomponents within the neurostimulator. IC 81 may be designed using the0.8 micron process in an effort to reduce the overall size and profileof the neurostimulator. IC 81 may operate substantially similar to IC 78of control module 72 (FIG. 15A). IC 81 includes a processor 82, a powermanager 84, a recharge module 85, a telemetry module 86, a pulsegenerator 88, and a clock 89.

Power manager 84 couples to rechargeable battery 90 to provide power toprocessor 82, recharge module 85, telemetry module 86, and pulsegenerator 88. Recharge module 85 couples to recharge and telemetry coil96 and receives power via coil 96 to recharge battery 90. Telemetrymodule 86 also couples to recharge and telemetry coil 96 and receivesstimulation programs and other instructions from a programmer operatedby the patient or physician via coil 96. Filter, power management,telemetry components 97 couple to telemetry module 86 to supportreliable wireless communication. Examples of filter, power managementand telemetry components 97 include a telemetry tank capacitor, voltageregulation filters, power supply filters, and battery bypass capacitors.Telemetry module 86 then provides the received stimulation programs toprocessor 82, which stores the programs in memory (not shown).

Crystal oscillator 98 is coupled to clock 89, which clocks processor 82to run the stimulation programs. Processor 82 directs pulse generator 88to provide stimulation to the electrodes of the neurostimulator viastimulation conductors 92. Processor 82 directs pulse generator 88according to the stimulation programs received from telemetry module 86and the clock cycle received from clock 89. Pulse generator 88 iscoupled to stimulation capacitors and inductors 94, which includecapacitors to store stimulation pulses.

FIG. 17 illustrates another neurostimulator 100 that provides on-sitetreatment of neuralgia experienced by a patient. Neurostimulator 100 maysubstantially conform to the neurostimulators shown in FIGS. 9A-16. Forexample, neurostimulator 100 can be subcutaneously implanted at astimulation site adjacent a neuralgic region of the patient.Neurostimulator 100 comprises a housing 101 that houses a control module102, a battery 104, and a coil 106.

Neurostimulator 100 also includes two or more electrodes 103, 105 toprovide stimulation to the neuralgic region of the patient. Controlmodule 102 receives power from battery 104 to drive the electrodes 103,105 according to a stimulation program included in control module 102.The electrodes 103, 105 may alternatively include an array of electrodesthat provides enhanced stimulation programming flexibility. The array ofelectrodes may be integrated on housing 101 of neurostimulator 100.

Housing 101 conforms to a substantially cylindrical form factor and mayinclude ring electrodes along a length of housing 101. Housing 101 mayconform to a miniaturized form factor with a small diameter in order tofit directly adjacent the neuralgic region of the patient. Housing 101may also comprise a degree of curvature to conform to a radius of thestimulation site.

Housing 101 may be pre-formed with a degree of curvature. As illustratedin FIG. 17, housing 101 has a joint 107. In some embodiments, housing101 may permit the physician to bend the housing to a degree ofcurvature appropriate for a specific stimulation site. For example,housing 101 may comprise a flexible material or include bellows,illustrated in FIGS. 19 and 20, that allow housing 101 to bend.

In some embodiments, housing 101 may also define a hole 108 thatoperates in conjunction with either an insertion hook for implantationor removal hook for explantation. The physician may insertneurostimulator 100 at the stimulation site adjacent the neuralgicregion of the patient by engaging a tool with hook 108 and feedingneurostimulator 100 into the stimulation site. In order to removeneurostimulator 100 from the stimulation site, the physician may againuse the tool to engage hole 108 and pull neurostimulator 100 out of thepatient.

As in the examples of FIGS. 9A-15, battery 104 of neurostimulator 100may comprise a rechargeable battery with a capacity of at least 20milliamp-hours, more preferably at least 25 milliamp-hours, and stillmore preferably at least 30 milliamp-hours. Control module 102 iscoupled to coil 106, which operates as both a recharge coil and atelemetry coil

FIG. 18 is a schematic diagram illustrating a neurostimulator 101A inaccordance with an embodiment of the invention. Neurostimulator 100Acomprises a housing 101A, which defines a hole 108. Neurostimulator 100Ais substantially similar to neurostimulator 100 from FIG. 18.Neurostimulator 100A includes an array of ring electrodes 110 integratedalong housing 101A. Ring electrodes 110 may extend entirely or partiallyaround a circumference of housing 101A. Each of electrodes 110 iscoupled to control module 102 within housing 101A. The physician mayimplant neurostimulator 100A at the selected stimulation site with thearray of electrodes 110 directly adjacent the neuralgic region of thepatient. The array of electrodes 110 allows the physician or clinicianflexibility in programming the stimulation provided by neurostimulator100

FIG. 19 is a schematic diagram illustrating a neurostimulator 101B inaccordance with another embodiment of the invention. Neurostimulator100B is substantially similar to neurostimulator 100 of FIG. 17.Neurostimulator 100B comprises a first housing portion 112 and a secondhousing portion 114. First and second housing portions 112 and 114 areconnected by a bellows-like joint 113. Neurostimulator 100B includes anarray of ring electrodes 116 integrated along first housing portion 112and second housing portion 114. First and second housing portions 114may be formed from a variety of materials such as titanium, stainlesssteel, ceramic material, silicone, polyurethane or other polymericmaterials.

Each of electrodes 116 is coupled to control module 102 withinneurostimulator 100B. The physician may implant neurostimulator 100B atthe selected stimulation site with the array of electrodes 116 directlyadjacent the neuralgic region of the patient. First and second housingportions 112 and 114 may conform to a substantially miniaturized formfactor and a small diameter to fit within the stimulation site. Forexample, the stimulation site may be located in the back of the neck ofthe patient for neurostimulator 100B to treat occipital neuralgia.

As illustrated in FIG. 19, neurostimulator 100B includes bellows-likejoint 113 that allows bending of neurostimulator 100B. FIG. 20 is aschematic diagram illustrating neurostimulator 100B in a slightly bentposition to better conform to an implantation site. For example, thephysician may bend neurostimulator 100B about bellows-like joint 113 toa degree of curvature that conforms to a radius of the specificstimulation site. Bellows-like joint 113 may comprise titanium, nitinol,or another biocompatible material strong enough to withstand flexing.Bellows-like joint 113 may be substantially smaller relative toneurostimulator 100B if the material of bellows 113 is able to withstandthe increased flexing force.

Various embodiments of the invention have been described. The foregoingdescription of the exemplary embodiments of the invention has beenpresented for the purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Many modifications and variations are possible in light ofthe above teaching.

For example, although application of various embodiments of theinvention to occipital neuralgia has been described for purposes ofillustration, the invention may be applied to treat a variety ofdisorders. It is intended that the scope of the invention be limited notwith this detailed description, but rather by the claims. These andother embodiments are within the scope of the following claims.

1. A method comprising: applying transcutaneous electricalneurostimulation to multiple stimulation regions on an epidermal surfaceadjacent a neuralgic region of a patient; selecting one of thestimulation regions based on perceived efficacy of the transcutaneouselectrical neurostimulation in the selected stimulation region; applyingpercutaneous electrical neurostimulation to multiple stimulation siteswithin the selected stimulation region; and selecting one of thestimulation sites based on perceived efficacy of the percutaneouselectrical neurostimulation in the selected stimulation site.
 2. Themethod of claim 1, wherein selecting one of the stimulation regionsbased on perceived efficacy includes selecting one of the stimulationregions based on patient, and selecting one of the stimulation sitesbased on perceived efficacy includes selecting one of the stimulationsites based on patient feedback.
 3. The method of claim 1, whereinapplying transcutaneous electrical neurostimulation includes applyingthe transcutaneous electrical neurostimulation via an array ofelectrodes distributed on a patch applied to the epidermal region. 4.The method of claim 1, further comprising performing imaging to selectthe epidermal region.
 5. The method of claim 1, wherein applyingpercutaneous electrical neurostimulation includes applying thepercutaneous electrical neurostimulation via an array of electrodeneedles that penetrate the epidermal region.
 6. The method of claim 1,further comprising subcutaneously implanting a temporary neurostimulatorat the selected stimulation site to provide temporary electricalneurostimulation to the patient for evaluation of the efficacy of thetemporary electrical neurostimulation at the stimulation site.
 7. Themethod of claim 6, wherein the temporary neurostimulator is batteryoperated and has a battery lifetime of at least one day.
 8. The methodof claim 1, further comprising determining whether to subcutaneouslyimplant a chronic neurostimulator at the selected stimulation site basedon the efficacy of the temporary electrical neurostimulation.
 9. Themethod of claim 8, further comprising subcutaneously implanting thechronic neurostimulator.
 10. The method of claim 1, applying thetranscutaneous electrical neurostimulation and the percutaneouselectrical neurostimulation to alleviate symptoms of occipitalneuralgia.
 11. A neurostimulation screening device comprising: atranscutaneous electrical neurostimulation electrode array forapplication to an epidermal region adjacent a neuralgic region of apatient; and a controller coupled to the transcutaneous electricalneurostimulation electrode array to selectively apply stimulation energyto different combinations of electrodes within the array at differentstimulation regions, and record patient feedback relating to perceivedefficacy of the different combinations.
 12. The screening device ofclaim 11, wherein the transcutaneous neurostimulation electrode arraycomprises an electrode array patch having an adhesive layer forattachment to the epidermal region.
 13. The screening device of claim11, wherein the controller comprises a joystick input device to selectthe different combinations of electrodes in response to up, down, left,or right movements.
 14. The screening device of claim 13, wherein thecontroller comprises at least one input medium to mark one or more ofthe stimulation regions when the patient feedback is favorable.
 15. Thescreening device of claim 14, wherein the controller presents the markedstimulation region for selection by a user.
 16. The screening device ofclaim 14, wherein the controller selects the stimulation region from themarked stimulation regions.
 17. The screening device of claim 14,wherein the controller records the patient feedback, and the patientfeedback includes a pain assessment.
 18. The screening device of claim11, wherein the transcutaneous electrical neurostimulation electrodearray is sized to cover a substantial portion of a back of a neck of apatient.
 19. The screening device of claim 11, wherein thetranscutaneous electrical neurostimulation electrode array is shaped togenerally conform to a substantial portion of a back of a neck of apatient.
 20. A neurostimulation screening device comprising: an array ofpercutaneous needle electrodes for penetration of an epidermal regionadjacent a neuralgic region of a patient; and a controller coupled tothe needle electrodes to selectively apply stimulation energy todifferent combinations of the needle electrodes within the array atdifferent stimulation sites.
 21. The screening device of claim 20,wherein the controller includes an input device to record patientfeedback relating to perceived efficacy of the different combinations.22. The screening device of claim 20, wherein the controller comprises ajoystick input device to select the different combinations of needleelectrodes in response to up, down, left, or right movements.
 23. Thescreening device of claim 20, wherein the controller comprises at leastone input medium to mark one or more of the stimulation sites when thepatient feedback is favorable.
 24. The screening device of claim 23,wherein the controller presents the marked stimulation site forselection by a user.
 25. The screening device of claim 23, wherein thecontroller selects the stimulation site from the marked stimulationsites.
 26. The screening device of claim 20, wherein the controllerincludes an input device to record patient feedback relating toperceived efficacy of the different combinations, and wherein thecontroller records the patient feedback, and the patient feedbackincludes a pain assessment.
 27. A neurostimulation screening devicecomprising: a transcutaneous electrical neurostimulation electrode arrayfor application to an epidermal region adjacent a neuralgic region of apatient; an array of percutaneous needle electrodes for penetration ofthe epidermal region adjacent the neuralgic region of a patient; and acontroller to selectively apply stimulation energy to differentcombinations of electrodes within the transcutaneous electricalneurostimulation electrode array at different stimulation regions, andselectively apply stimulation energy to different combinations of theneedle electrodes within the array at different stimulation sites withinone of the stimulation regions.